Subversion Repositories zipcpu

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;
; Filename:     helloworld.S
;
; Project:      Zip CPU -- a small, lightweight, RISC CPU soft core
;
; Purpose:      A test of whether or not we can scroll a message on a
;               seven segment display.  This depends upon the seven segment
;               display driver (not included) being installed at position
;               0x15 in memory.  If so, this scrolls the message:
;               "HELLO UJorld." across the 4 seven segment display digits.
;
;               This test discovered that right shifting by 31 or more did
;               not result in zero as desired.  It also discovered that the
;               .DAT assembly instruction did not function as desired.  Both
;               bugs were fixed to get this to work.
;
; Creator:      Dan Gisselquist, Ph.D.
;               Gisselquist Technology, LLC
;
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;
; Copyright (C) 2015, Gisselquist Technology, LLC
;
; This program is free software (firmware): you can redistribute it and/or
; modify it under the terms of  the GNU General Public License as published
; by the Free Software Foundation, either version 3 of the License, or (at
; your option) any later version.
;
; This program is distributed in the hope that it will be useful, but WITHOUT
; ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
; FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
; for more details.
;
; License:      GPL, v3, as defined and found on www.gnu.org,
;               http://www.gnu.org/licenses/gpl.html
;
;
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;
; Register map
;       R12 peripherals
;       R11  timer length
;       R10  value to clear/reset the PIC
;       uR12 = memory
;       uR11 = rawsseg
;       uR9  = state
;       R8   = new value for SSEG
build_supervisor_state:
        CLR     R12             ; Load a pointer to our peripherals
        LDIHI   $c000h,R12
        LDI     $5f5e1h,R11     ; An amount to reset the timer to: 1/4 sec
        LSL     $6,R11
        LDIHI   $8010h,R10      ; A value to clear/reset the PIC for timerA ints
        LDILO   $ffffh,R10
        MOV     $1+PC,uR12      ; User memory (so this isn't supervisor state..)
        BRA     $4
        .DAT    $0x6e9e1c1c     ; Raw SSEG for 'HELL'
        .DAT    $0xfc007c70     ; Raw SSEG for 'O UJ'
        .DAT    $0x3a0a607b     ; Raw SSEG for 'orld.'
        .DAT    $0x00000000     ; Raw SSEG for '    '
build_user_state:
        LDI     $15h,R0
        MOV     R0,uR11
        MOV     $6+PC,uPC
        CLR     R0
        MOV     R0,uR9
repeat:
        STO     R11,$4(R12)     ; Reset the timer
        STO     R10,(R12)       ; Reset the PIC
        RTU
        BRA     $-4
user_task:
        MOV     R9,R0
        LSR     $2,R0
        ADD     R12,R0
        LOD     (R0),R8         ; Read the left word
        MOV     R9,R1           ; Rotate it into place
        AND     $3,R1
        LSL     $3,R1           ; Multiply by eight
        LSL     R1,R8           ; Shift words to left by 0,8,16,24 bits

        ADD     $1,R0           ; Calculate address of next word
        CMP     $4+R12,R0
        SUB.GE  $4,R0
        LOD     (R0),R2         ; Load the next word into a building location
        LDI     $32,R3
        SUB     R1,R3
        LSR     R3,R2
        OR      R2,R8           ; Put the two together

        STO     R8,(R11)        ; Store the result

        ADD     $1,R9           ; Increment our state
        AND     $15,R9

        WAIT                    ; Wait for the next interrupt
        BRA     $-21            ; Back up to the top to start over

        BREAK
        BREAK
        BREAK